Biology Chapter 10: Homeostasis Flashcards
Excretory system
serves many functions, including the regulation of blood pressure, blood osmolarity, acid-base balance
kidney
produces urine, which dumps into the ureter at the renal pelvis.
Bladder
collects urine until it is excreted through the urethra
Kidney contains
a cortex and a medulla - each kidney has a hilum which contains a renal artery, renal vein and ureter.
Portal system
a circuit of blood in which there are two capillary beds in tandem connected by an artery or vein; examples include the hypophyseal, hepatic and renal portal system.
Blood from the renal artery flows into..
the afferent arterioles, which form glomeruli in Bowman’s capsule (the first capillary bed).
Blood flows from Bowman’s capsule into..
the efferent arteriole to the vasa recta, which surround the nephron (the second capillary bed), before leaving the kidney through the renal vein.
Detrusor muscle
muscular lining of the bladder. It is under parasympathetic control.
Internal urethral sphincter
consists of smooth muscle and is under involuntary (parasympathetic) control.
external urethral sphincter
consists of skeletal muscle and is under voluntary control
Kidney participates in solute movement through three processes:
- Filtration
- Secretion
- Reabsorption
Filtration
movement of solutes from blood to filtrate at Bowman’s capsule. The direction and rate of filtration is determined by Starling forces, which account for the hydrostatic and oncotic pressure differentials between the glomerulus and Bowman’s space
Secretion
the movement of solutes from blood to filtrate anywhere other than Bowman’s capsule
Reabsorption
the movement of solutes from filtrate to blood
Proximal convoluted tubule
site of bulk reabsorption of glucose, amino acids, soluble vitamins, salt and water. It is also the site of secretion for hydrogen ions, potassium ions, ammonia and urea
descending limb of the loop of Henle
permeable to water, but not sale; therefore as the filtrate moves into the more osmotically conventrated renal medulla, water is reabsorbed from the filtrate.
Countercurrent multiplier
created by the vasa recta and the nephron flowing in opposite directions - allows for maximal reabsorption.
Acsending limb of the loop of Henle
permeale to salt, but not to water; therefore, salt is reabsorbed both passively and actively.. The diluting segment is in the outer medulla; because salt is actively reabsorbed in this site, the filtrate actually becomes hypotonic compared to the blood.
collecting duct
responsive to both aldosterone and antidiuretic hormone and has variable permeability, which allows reabsorption of the right amount of water depending on the body’s needs.
When blood pressure and volume are low, what hormonal systems are activated?
aldosterone, antidiuretic hormone
Aldosterone
steroid homone
regulated by the renin-angiotensis-aldosterone system that increases sodium reabsorption in the DCT and collecting duct, increasing water reabsorption.
Results in increased volume but not change in osmolarity
Antidiuretic hormone
peptide hormone synthesized by the hypothalamus and released by the posterior pituitary. Its release is stimulated not only by low blood volume, but also by high blood osmolarity.
Increases permeability of the collecting duct to water, increasing water reabsorption.
Results in increased blood volume and a decreased blood osmolarity.
How can the kidney regulate pH?
Selective reabsorption or secretion of bicarbonate or H+
What are the three layers of the skin?
hypodermis, dermis and epidermis
What are the five layers of the epidermis?
stratum basale stratum spinosum stratum granulosum stratum lucidum stratum corneum
What is the stratus basale made of?
stem cells that proliferate to form keratinocytes.
Where are keratinocyte nuclei lost?
the stratum granulosum
What forms in the are in the stratum corneum?
many thin layers.
Melanocytes
produce melanin, which protects the skin from DNA damage caused by ultraviolet radiation; melanin is passed to keratinocytes.
Langerhans cells
special macrophages that serve as antigen resenting cells in the skin.
What are the two layers of the dermis?
papillary and reticular
Merkel cells
sensory - deep pressure and texture
Free nerve endings
sense pain
Meissner’s corpuscles
sense light touch
Ruffini endings
sense stretch.
Pacinian corpuscles
sense deep pressure and vibration
The hypodermis contains
fat and connective tissue and connects the skin to the rest of the body.
Cooling mechanisms of the skin
sweating, which absorbs heat from the body through evaporation of water from sweat and vasodilation. Sweat glands are innervated by postganglionic cholinergic sympathetic neurons
Warming mechanisms
Include piloerection, in which arrector pili muscles contract causing hairs to stand on end, vasoconstriction, shivering, and insulation provided by fat.
